JP2017080705A - Unwoven fabric filter medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unwoven fabric filter medium capable of being equipped with particulate dust capturing performance, long longevity, and ventilation resistance in a well-balanced manner.SOLUTION: An unwoven fabric filter medium 1 is a multilayer-structured unwoven fabric filter medium with a density gradient having a coarse layer part 2 located on the upstream side and a dense layer part 3 located on the downstream side. Ultrafine fiber assemblies 4, 4 consisting mainly of ultrafine fibers are integrated in the coarse layer part 2, or in adjacency with the coarse layer part 2. At least a part of the ultrafine fibers 41, 41 of the ultrafine fiber assemblies 4 enter the coarse layer part 2 to make an entanglement of fibers constituting the coarse layer part with the entered ultrafine fibers 41, so that the ultrafine fibers are arranged three-dimensionally in the coarse layer part 2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-woven filter medium. It is related with the nonwoven fabric filter material especially used for filtration of the dust in the air.

Nonwoven fabric filter materials are used for air filtration as air filters for internal combustion engines and various ventilation devices used in automobiles and the like. In such applications, it is required to efficiently remove fine dust from a large amount of air. Nonwoven filter media are required to have high cleaning efficiency, long life that can remove dust without clogging for a long period of time, and compactness that can exhibit sufficient filtration performance in a limited space. .

Particularly in recent years, these air filters are required to have improved performance for removing fine dust such as carbon dust. If the removal of fine dust such as carbon dust is insufficient, dust accumulates on the detection device such as a flow sensor located downstream of the filter medium (filter element), and the accuracy and stability of the output of the detection device This is because the sex may be insufficient.

In a conventionally known non-woven filter medium, fine particle dust such as carbon dust is often captured in a layer having the highest density and a small fiber diameter as long as the filter medium has a multilayer structure. Therefore, when carbon dust is captured, the pressure loss of the filter medium is likely to increase, and the life is shortened. In particular, if the trapping efficiency (cleaning efficiency) of the fine particle dust is increased by increasing the density of the dense layer, the filter medium is more easily clogged. That is, in the nonwoven fabric filtering material, there is a trade-off relationship between the cleaning efficiency and the life of the filtering material for the fine particle dust.

In the field of air conditioners, filter media such as so-called cabin filters and HEPA filters are used for the purpose of capturing fine dust (particulate dust). In such a filter, in order to improve the trapping performance of the particulate dust, a filter medium composed of a thin fiber layer using a charged fiber or ultrafine fiber and having a high density is used. Since such a filter medium is difficult for air to pass through, a filter is configured with a large filtration area by taking a folded structure with a reduced pitch interval. However, in order to use these filter media as filter media for air cleaners for automobile engines, the flow rate in these applications is large, and thus the filter element tends to be enlarged. In addition, since such a filter medium has a thin fiber layer, it is difficult to be resin-molded by fitting it in a mold, and there are many restrictions in maintaining a predetermined weave shape.

Various attempts have been made to construct nonwoven fabrics with ultrafine fibers that are advantageous for capturing fine particle dust. However, in the ultrafine fiber nonwoven fabrics obtained by a general-purpose melt-blowing method, the ultrafine fibers are arranged in a plane and are three-dimensional. It is difficult to produce a thick nonwoven fabric having a mechanical structure. In addition, the conventional dry manufacturing method for nonwoven fabrics makes it difficult to spin and mix ultrafine fibers due to problems such as dispersion and tearing, and the thickness of the filter media can also be reduced by wet manufacturing and airlaid methods. It is difficult to take.

A technique in which an ultrafine fiber nonwoven fabric excellent in capturing characteristics of fine particles and a nonwoven fabric composed of other fibers is also known.
For example, Patent Document 1 discloses a nonwoven fabric filtering material in which a melt blown nonwoven fabric having an average fiber diameter of 1 to 8 μm and a spunbond nonwoven fabric having an average fiber diameter of 10 to 30 μm are bonded and integrated, and the nonwoven fabric filtration is performed. According to the material, it is disclosed that a non-woven filter material for air filter excellent in dust capturing performance and mechanical properties can be obtained.

JP 2007-125546 A

The nonwoven fabric filtering material disclosed in Patent Document 1 is intended to capture fine particle dust by a layer of melt blown nonwoven fabric having an average fiber diameter of 1 to 8 μm, but it is intended to improve the capture performance (cleaning efficiency) of fine particle dust. For example, the density of the meltblown nonwoven fabric must be increased, and as a result, the life of the filter medium must be sacrificed. That is, the nonwoven fabric filtering material disclosed in Patent Document 1 also does not essentially solve the trade-off relationship between the capture performance and the life regarding the fine particle dust. Moreover, in the nonwoven fabric filtering material disclosed in Patent Document 1, increasing the density of the melt blown nonwoven fabric to increase the particulate dust capturing performance (cleaning efficiency) increases the airflow resistance of the nonwoven fabric filtering material. Also occurs.

An object of the present invention is to provide a nonwoven fabric filtering material that can have a good balance of fine particle dust trapping performance (cleaning efficiency), long life, and ventilation resistance.

As a result of intensive studies, the inventor has found that in the conventional nonwoven fabric filtering material, the ultrafine fibers for capturing the particulate dust are arranged in an extremely thin layer, and therefore, in order to increase the cleaning efficiency, the ultrafine fiber layer As a result, it was found that the relationship between the life and the ventilation resistance deteriorated. The ultrafine fibers are arranged in a very thin layer because there are great restrictions due to the production method of the ultrafine fibers, and it is difficult to arrange the ultrafine fibers in a three-dimensional manner over a predetermined thickness.

Then, the inventor conducted further earnest studies and combined the ultrafine fibers with the fibers constituting the normal nonwoven fabric, and in the coarse layer portion of the nonwoven fabric having a dense density gradient, the ultrafine fibers were entangled with the fibers of the coarse layer portion. The inventors have found that the above problems can be solved by arranging the ultrafine fibers in three dimensions, and have completed the present invention.

The present invention is a nonwoven fabric filtering material having a multi-layer structure having a density gradient having a coarse layer portion located on the upstream side and a dense layer portion located on the downstream side, wherein the coarse layer portion or the coarse layer A fine fiber assembly mainly composed of fine fibers is integrated adjacent to the portion, and at least a part of the fine fiber of the fine fiber assembly enters the coarse layer portion to form the coarse layer portion. And the ultrafine fibers that have entered are entangled so that the ultrafine fibers are arranged three-dimensionally in the coarse layer portion (first invention).

In the first invention, it is preferable that the ultrafine fiber aggregate is a fiber aggregate substantially composed of only ultrafine fibers (second invention). Alternatively, in the first invention, at least a part of the ultrafine fiber assembly is fragmented and integrated in an island shape with respect to the coarse layer portion, and a part of the ultrafine fiber assembly is inside the coarse layer portion. It is preferable to enter (third invention). Alternatively, in the first invention, it is preferable that the ultrafine fiber does not substantially enter the dense layer portion (fourth invention).

The nonwoven fabric filtering material of the present invention (the first invention) has a good balance of trapping performance, long life and ventilation resistance against fine particle dust such as carbon dust.

Furthermore, if it is made like 2nd invention or 3rd invention, the capture performance with respect to fine particle dust, long life property, and ventilation resistance will become favorable more effectively. In addition, if it is further configured as in the fourth invention, the effect of improving the life is particularly enhanced.

It is a schematic diagram which shows the cross-section of the nonwoven fabric filter material of 1st Embodiment of invention. It is a schematic diagram which shows the cross-section of the nonwoven fabric filter material of 2nd Embodiment of invention. It is a schematic diagram which shows the manufacturing process of the nonwoven fabric filter material of 1st Embodiment of invention. It is a schematic diagram which shows the manufacturing process of the nonwoven fabric filter material of 2nd Embodiment of invention.

Hereinafter, embodiments of the invention will be described with reference to the drawings, taking as an example a non-woven filter material that can be used as a filter material of an air cleaner for filtering air supplied to an automobile engine. The invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

Drawing 1 is a mimetic diagram showing the section structure of the nonwoven fabric filter material of a 1st embodiment of the invention. The nonwoven fabric filtering material of this embodiment is a sheet-like nonwoven fabric, and when used for an air cleaner of an automobile engine, it is usually used as a filter element member fixed to a frame in a folded state.

The nonwoven fabric filtering material 1 is a nonwoven fabric filtering material having a multi-layer structure having a density gradient having a rough layer portion 2 located on the upstream side and a dense layer portion 3 located on the downstream side. The change in density may change discontinuously for each layer, or may change continuously from the upstream side toward the downstream side. Moreover, in this embodiment, the nonwoven fabric filter material 1 has a two-layer structure of the rough layer portion 2 and the dense layer portion 3, but may have a three-layer structure or more. In the case of a multilayer structure of three or more layers, other layers can be provided on the upstream side of the coarse layer portion, between the coarse layer portion and the dense layer portion, or on the downstream side of the dense layer portion. Preferably, each layer is laminated so as to gradually become dense from the upstream side toward the downstream side. Preferably, the coarse layer portion 2 is provided so as to be located on the most upstream side. In FIG. 1, the upper side of the figure is the upstream side, and the lower side of the figure is the downstream side. The same applies to FIG. 2, FIG. 3, and FIG.

The coarse layer portion 2 is a layer in which the density of the nonwoven fabric is made coarser than that of the dense layer portion 3. The coarse layer portion 2 captures most of the dust such as JIS8 dust. The coarse layer portion 2 contributes to an improvement in the amount of dust trapped with respect to the general dust of the nonwoven fabric filter material (lifetime of the filter material). A preferable space ratio of the coarse layer portion 2 is about 90 to 99%. Here, the space ratio of the nonwoven fabric layer is a value indicating the volume of space per unit volume of the nonwoven fabric layer (volume obtained by subtracting the volume occupied by fibers from the volume occupied by the whole nonwoven fabric layer). That the nonwoven fabric layer is coarse means that the space ratio is large, and that the nonwoven fabric layer is dense means that the space ratio is small.

The dense layer portion 3 is a layer in which the density of the nonwoven fabric is made denser than that of the coarse layer portion 2. The dense layer portion 3 prevents dust such as JIS8 dust from passing through the nonwoven fabric filtering material 1. That is, the dense layer part 3 contributes to the improvement of the cleaning efficiency with respect to the general dust of the nonwoven fabric filtering material. A preferable space ratio of the dense layer portion 3 is about 80 to 95%.

The fibers constituting the coarse layer portion 2 and the dense layer portion 3 may be natural fibers, but synthetic fibers are preferably used. Synthetic fibers include, for example, polyesters such as PET (polyethylene terephthalate), PBT (polybutylene terephthalate) and PTT (polytrimethylene terephthalate), polyolefins such as PP (polypropylene) and PE (polyethylene), 6-nylon and Examples thereof include fibers manufactured from resin raw materials such as PA (polyamide) such as 66-nylon and polyacrylic, and rayon fibers. These synthetic fibers constitute the rough layer portion 2 and the dense layer portion 3 alone or in combination with other fibers. The coarse layer portion 2 and the dense layer portion 3 may contain so-called low melting point fibers so that the thermal bond method can be used.

The thickness of the fibers constituting the coarse layer portion 2 and the dense layer portion 3 is not particularly limited, but preferably the dense layer portion so that the average fiber diameter of the fibers constituting the coarse layer portion 2 is 15 to 35 μm. 3 is made to have an average fiber diameter of 5 to 20 μm. It is preferable that the coarse layer portion 2 is thicker than the dense layer portion so that the coarse layer portion 2 is bulkier than the dense layer portion 3.

Other specific specifications and characteristics of the coarse layer portion 2 and the dense layer portion 3 are not particularly limited, but are preferably in the following ranges. The basis weight of the coarse layer portion 2 is preferably 30 to 150 g / square m, and the basis weight of the dense layer portion 3 is preferably 100 to 250 g / square m.

Furthermore, ultrafine fiber aggregates 4, 4 mainly composed of ultrafine fibers 41 are integrated with the nonwoven fabric filtering material 1. Here, in the present invention, the ultrafine fiber means a fiber having a fiber diameter of 5 μm or less. The ultrafine fiber is typically obtained by a melt blow method or an electrospinning method. Examples of the resin constituting the ultrafine fiber include polypropylene resin and polyethylene terephthalate resin. The ultrafine fiber assembly 4 is mainly composed of ultrafine fibers, and the ultrafine fibers are gathered by being entangled in a non-woven fabric. As will be described later, a melt blown nonwoven fabric of ultrafine fibers produced by a meltblowing method or a non-woven fabric of ultrafine fibers produced by an electrospinning method is unraveled by a needle punch or the like so that an ultrafine fiber assembly mainly composed of ultrafine fibers 41 is obtained. The ultrafine fiber assembly 4 is integrated with the nonwoven fabric filtering material 1. In FIG. 1 (the same applies to FIGS. 2, 3, and 4), the cross-sectional outline is shown on the assumption that the ultrafine fiber assembly 4 is thick, and a part of the fine fiber 41 is indicated by a solid line.

In the nonwoven fabric filtering material 1, the ultrafine fiber aggregates 4 and 4 and the ultrafine fibers 41 and 41 contribute to capturing fine particle dust such as carbon dust. From the viewpoint of enhancing the capturing performance of the fine particle dust, the ultrafine fiber aggregates 4 and 4 and the ultrafine fibers 41 and 41 may be subjected to electret treatment.

The ultrafine fiber assemblies 4 and 4 are integrated into the coarse layer portion 2 in the coarse layer portion 2 or adjacent to the coarse layer portion 2. When the ultrafine fiber assembly 4 is small and fragmented, the fragmented ultrafine fiber assembly may enter the rough layer portion 2 and be integrated. When the ultrafine fiber assembly 4 has a planar shape with a certain size, the ultrafine fiber assembly is integrated adjacent to the coarse layer portion 2. When the ultrafine fiber assembly is fragmented to a large size, a part of the ultrafine fiber assembly exists adjacent to the coarse layer part, but a part of the ultrafine fiber assembly is in the coarse layer part. In some cases, it can be integrated.

The integration of the ultrafine fiber assemblies 4, 4 and the coarse layer portion 2 is such that at least a part of the ultrafine fibers 41, 41 constituting the ultrafine fiber assemblies 4, 4 enters the coarse layer portion 2 to form the coarse layer portion. This is done by entanglement of the constituent fibers and the ultrafine fibers that have entered. As will be described later in the manufacturing method, the ultrafine fibers 41 are pulled by the needle of the needle punch, guided into the coarse layer portion 2, and entangled with the fibers constituting the coarse layer portion. Therefore, in the coarse layer part 2, the ultrafine fibers 41 and 41 are also extended in the direction orthogonal to the nonwoven fabric layer. Further, in a portion where a part of the ultrafine fiber assembly 4 has entered the coarse layer portion 2, the portion of the ultrafine fiber assembly extends in a direction intersecting with the nonwoven fabric layer. In this case, the fibers constituting the coarse layer portion being caught by the ultrafine fiber assembly that has entered the coarse layer portion also contributes to the fixation of the ultrafine fiber assembly 4. As described above, in the coarse layer portion 2 of the nonwoven fabric filtering material 1, the ultrafine fibers 41 are three-dimensionally arranged in the coarse layer portion over a predetermined thickness.

The form in which the ultrafine fiber assembly 4 is integrated with the coarse layer portion 2 is that the ultrafine fiber 41 extending from the ultrafine fiber assembly 4 is the coarse layer portion while the ultrafine fiber assembly 4 maintains the surface shape of the melt blown nonwoven fabric. It may be in the form of entering 2 and entangled. Such a form is easy to be realized when there are few needle punches. More preferably, more needle punches are performed to promote fragmentation of the melt-blown nonwoven fabric so that at least a part of the ultrafine fiber aggregate is fragmented and integrated into an island shape with respect to the coarse layer portion. Good. In addition, it is preferable that a part of the ultrafine fiber assembly enters the inside of the coarse layer portion with the fragmentation of the ultrafine fiber assembly. A more preferable configuration of the ultrafine fibers can be realized by fragmenting the ultrafine fiber aggregate and entering the coarse layer portion.

Although the ultrafine fiber assembly 4 may include fibers that are not ultrafine fibers, the ultrafine fiber assembly is preferably a fiber assembly that is substantially composed of only ultrafine fibers. The higher the proportion of the ultrafine fibers in the ultrafine fiber assembly, the better the particulate dust capturing performance. Further, the higher the proportion of the ultrafine fibers in the ultrafine fiber assembly, the more easily the ultrafine fiber assembly is loosened and fragmented, and the ultrafine fiber assemblies 4 and 4 and the ultrafine fibers 41 and 41 are three-dimensionally in the coarse layer portion 2. Easier to place.

In addition, it is preferable that the ultrafine fibers 41 and 41 are allowed to enter the coarse layer portion 2 while the dense fiber portion 3 does not substantially enter the dense layer portion 3. This is because if the fine fiber is provided in the dense layer portion, the dense layer portion is easily clogged with carbon dust. Such a configuration can be achieved by adjusting the depth and direction of the needle punch.

Specifically, in the first embodiment, the nonwoven fabric filtering material 1 has a two-layer structure of a coarse layer portion 2 and a dense layer portion 3 made of PET fiber, the coarse layer portion 2 is located on the upstream side, and the downstream side. The dense layer portion 3 is located in The average fiber diameter in the coarse layer portion 2 is 23 μm, the space ratio is 96%, and the basis weight is 75 g / square m. The average fiber diameter in the dense layer portion 3 is 13 μm, the space ratio is 92%, and the basis weight is 160 g / square m. is there. Further, as the ultrafine fiber aggregates 4 and 4, ultrafine fiber aggregates derived from a melt blown nonwoven fabric made of PP resin and having an average fiber diameter of 3 μm are integrated on the upstream side of the coarse layer portion 2.

The non-woven filter medium 1 can be used for air filtration as a so-called dry filter medium without oil. It is also possible to use so-called wet filter media and viscous filter media with oil, etc., but if oil adheres to ultrafine fibers that contribute to capturing particulate dust such as carbon dust, the particulate dust capturing performance will decline, It is preferable to use at least the coarse layer portion 2 and the ultrafine fiber assembly 4 as a dry filter medium without oil.

The manufacturing method of the nonwoven fabric filter material 1 of 1st Embodiment is demonstrated with FIG. The nonwoven fabric filtering material 1 includes a first step of laminating the respective fiber aggregates to be the ultrafine fiber aggregate 4, the coarse layer portion 2, and the dense layer portion 3, and a specific needle punch or hydroentanglement treatment on the laminate. It is manufactured by the nonwoven fabric manufacturing method including the 2nd process of giving ultrafine fiber to a rough layer part by giving.

The first step will be described in detail. In the first step, a fiber assembly 6 mainly composed of ultrafine fibers manufactured by a melt blow method or an electrospinning method, a fiber assembly 21 to be a coarse layer portion, and a fiber assembly 31 to be a dense layer portion These layered fiber assemblies are laminated so as to include the fiber assembly 6, and the fiber assembly 6 mainly composed of ultrafine fibers is adjacent to the fiber assembly 21 to be the coarse layer portion.

As the fiber assembly 6 mainly composed of ultrafine fibers, a non-woven fabric of ultrafine fibers such as a melt blown nonwoven fabric of ultrafine fibers can be used. Alternatively, ultrafine fibers may be directly laminated on the fiber assembly 21 to be the coarse layer portion to form a web of ultrafine fibers. In the present embodiment, a melt blown nonwoven fabric of ultrafine fibers made of PP resin is used as the fiber assembly 6 mainly composed of ultrafine fibers. Use of a non-woven fabric made of ultrafine fibers is excellent in handleability. In addition, even fine fibers that are difficult to handle are easily distributed uniformly. In addition, in the fiber assembly 6 mainly composed of ultrafine fibers, if the coupling between the ultrafine fibers is too strong, the ultrafine fiber assembly 6 is fragmented and it is difficult for the ultrafine fibers to enter the coarse layer portion. It is preferable to prepare one having a weak bond between ultrafine fibers. For the same reason, the basis weight of the fiber aggregate 6 (extra fine fiber nonwoven fabric) mainly composed of ultrafine fibers is preferably 50 g / square m or less. If the basis weight is too large, the needle punching process in the second step is difficult. Become. In this embodiment, a melt blown nonwoven fabric of ultrafine fibers made of PP resin having a basis weight of 5 g / square m was used.

As the fiber assembly 21 to be the coarse layer portion and the fiber assembly 31 to be the dense layer portion, each layer may be prepared as a nonwoven fabric or a web. In the present embodiment, a nonwoven fabric having a two-layer structure of a coarse layer portion and a dense layer portion made of PET fibers was used as the fiber assembly 21 to be the coarse layer portion and the fiber assembly 31 to be the dense layer portion.

Layers of these fiber assemblies are laminated so that a fiber assembly (ultrafine fiber melt blown nonwoven fabric) 6 mainly composed of ultrafine fibers is adjacent to the fiber assembly 21 to be the coarse layer portion. Any of the positional relationship between the fiber assembly 21 to be the coarse layer portion and the fiber assembly 6 mainly composed of ultrafine fibers may be upstream. In this embodiment, from the upstream side toward the downstream side, the order of the fiber assembly 6 mainly composed of ultrafine fibers, the fiber assembly 21 to be a coarse layer portion, and the fiber assembly 31 to be a dense layer portion Each layer was laminated so as to be.

The 2nd process performed following the 1st process is explained in full detail. In the second step, needle punching or hydroentanglement is performed in a direction from the fiber assembly 6 mainly composed of ultrafine fibers to the fiber assembly 21 to be the coarse layer portion, and the ultrafine fibers are allowed to enter the coarse layer portion while being laminated. The obtained fiber assembly is integrated, and the laminate of the fiber assembly obtained in the first step is used as a nonwoven fabric having a rough layer portion and a dense layer portion. That is, in the second step, the ultrafine fibers contained in the fiber assembly 6 mainly composed of ultrafine fibers are caused to enter the interior of the fiber assembly 21 to be the coarse layer portion by needle punching or hydroentanglement, and the ultrafine fibers The assembly 4 is integrated with the coarse layer portion 2.

The direction in which the needle N is protruded in the needle punching process and the direction in which the water stream is jetted in the hydroentanglement process are directions from the fiber assembly 6 mainly composed of ultrafine fibers toward the fiber assembly 21 to be a coarse layer portion. is there. In the present embodiment, since the ultrafine fiber assembly is disposed on the upstream side of the coarse layer portion, a needle or a water flow is applied from the upstream side toward the downstream side.

In FIG. 3, the example which performed the 2nd process with the needle punch is shown. In FIG. 3A, from the upstream side toward the downstream side, the fiber assembly 6 mainly composed of ultrafine fibers, the fiber assembly 21 to be a coarse layer portion, and the dense layer portion are to be formed by the first step. A state in which the fiber assemblies 31 are sequentially laminated is shown. Needles N and N are hit from the upstream side where the fiber assembly 6 mainly composed of ultrafine fibers is disposed.

In the process of needle punching, the ultrafine fibers in the fiber assembly 6 mainly composed of ultrafine fibers are hooked by the barbs provided in the needle N and driven into the fiber assembly 21 to be the coarse layer portion. Go. In addition, since the ultrafine fibers are pulled by the needle N, a part of the ultrafine fibers are cut, the ultrafine fiber aggregate is loosened, or a hole is opened or broken in the ultrafine fiber aggregate. That is, by performing needle punching, the fiber assembly 6 (melt blown nonwoven fabric of ultrafine fibers) mainly composed of ultrafine fibers becomes perforated, fragmented, and gradually becomes finer. From this, the ultrafine fibers 41 are drawn into the coarse layer portion (FIG. 3B).

In this way, by applying the needle punch to the ultrafine fiber assembly 6, the ultrafine fiber of the ultrafine fiber assembly or the ultrafine fiber assembly itself is inserted into the coarse layer portion 2 and mixed. And the characteristic structure of the nonwoven fabric filter material 1 by which the ultrafine fiber assembly 4 was integrated with the coarse layer part 2, and the ultrafine fiber 41 was arrange | positioned three-dimensionally in the coarse layer part 2 (FIG. 3). (C)) In the description of the second step, the case of needle punching has been mainly described, but the same applies to the case of hydroentanglement.

In addition, about the process for making the fiber assembly 21 which should become a coarse layer part, and the fiber assembly 31 which should become a dense layer part into a coarse layer part and a dense layer part, respectively, a needle punch or heat What is necessary is just to add and implement | achieve well-known processes, such as the process of a press.

The operation and effect of the invention will be described.
According to the nonwoven fabric filtering material of the first embodiment, the ultrafine fiber assembly 4 mainly composed of ultrafine fibers is integrated in the coarse layer portion 2 or adjacent to the coarse layer portion 2. Since at least a part of the ultrafine fibers 41 of the fiber assembly 4 enter the coarse layer portion 2 and the fibers constituting the coarse layer portion 2 and the ultrafine fibers 41 that have entered are entangled, the ultrafine fibers 41 are coarse layers. It is arranged three-dimensionally in the part 2. Thereby, it becomes possible to capture the particulate dust at a portion with a high space ratio by the ultrafine fiber, and even if the capturing efficiency (cleaning efficiency) of the particulate dust is increased, it becomes a filter material that is not easily clogged (long life). Further, if the ultrafine fibers can be three-dimensionally arranged in a portion having a high space ratio, an increase in ventilation resistance can be suppressed.

In the prior art, for example, the technique described in Patent Document 1, the ultrafine fibers are integrated with the nonwoven fabric filtering material in the form of a melt blown nonwoven fabric. Since the ultrafine fiber is thin, even if it is a melt blown nonwoven fabric, it is usually only possible to have a very thin structure in which the fibers are arranged in a plane. Therefore, in the prior art, it is necessary to adopt a filtration form in which fine dust is captured by a very thin layer, and the cleaning efficiency is improved by increasing the density of the ultrafine fibers, and the service life and pressure loss are reduced. And had to be a trade-off.
On the other hand, in the nonwoven fabric filtering material 1 of the first embodiment, the ultrafine fibers 41 are three-dimensionally arranged in the coarse layer portion 2 and can be dispersed in the coarse layer portion to capture fine particle dust. It can be done.

In the nonwoven fabric filtering material 1 of the first embodiment, from the viewpoint of improving cleaning efficiency, long life, and low pressure loss, the ultrafine fiber aggregate may be a fiber aggregate substantially composed of only ultrafine fibers. preferable. The ultrafine fibers are easy to cut, and when the needle punching or the like is performed in the process of manufacturing the non-woven filter material 1, the ultrafine fiber aggregates are likely to be scattered or fragmented, and easily enter the coarse layer portion 2. This is because the arrangement of the fibers tends to have a more three-dimensional structure.

For the same reason, in the nonwoven fabric filtering material 1 of the first embodiment, at least a part of the ultrafine fiber aggregate 4 is fragmented and integrated with the coarse layer portion 2 in an island shape. It is preferable that a part of the aggregate 4 is in the coarse layer portion 2. If it is set as this form, a part of ultrafine fiber aggregate will disperse | distribute in the thickness direction of the coarse layer part 2, and an ultrafine fiber will come to be arrange | positioned more three-dimensionally.

In addition, if the ultrafine fibers 41 enter the dense layer portion 3, the dense layer portion 3 is likely to be clogged. Therefore, it is preferable to prevent the ultrafine fibers from substantially entering the dense layer portion. It is possible to improve the life and low pressure loss in a well-balanced manner, and is particularly effective for extending the life.

Moreover, according to the said manufacturing method, without using the special apparatus for arrange | positioning an ultrafine fiber in three dimensions, the nonwoven fabric filtration material by which the ultrafine fiber was arrange | positioned three-dimensionally by the combination of a conventional apparatus and process is obtained. Can be obtained. For example, it is possible to obtain a nonwoven fabric filtering material in which ultrafine fibers are three-dimensionally arranged using almost the same equipment as that for manufacturing a conventional laminated nonwoven fabric having a multilayer structure.

In the prior art, it has been possible to obtain only an extremely fine fiber aggregate in which fibers are arranged in a very thin plane. On the other hand, according to the above production method, such a thin ultrafine fiber assembly is used as an intermediate material, and is adjacent to the coarse layer portion and needle punched or hydroentangled to form the ultrafine fiber from the ultrafine fiber assembly. 41 can be pulled out and arranged three-dimensionally in the coarse layer portion 2. Further, if the ultrafine fiber aggregate is loosened by needle punching or hydroentanglement, and preferably a part thereof is fragmented so as to be inserted into the coarse layer portion 2, more fine fine particles are contained in the coarse layer portion 2. The fibers can be three-dimensionally arranged in a complicated arrangement form, which contributes to the improvement of the cleaning efficiency of the nonwoven fabric filter material, the extension of the service life, and the reduction of the low pressure loss.

In the prior art, for example, the technique described in Patent Document 1, a melt-blown nonwoven fabric made of thin flat ultrafine fibers is laminated on a dense nonwoven fabric layer and integrated by adhesion or fusion. With this, it was only possible to arrange the ultrafine fibers in a planar shape. Further, in the prior art, it was considered that the melt blown nonwoven fabric of ultrafine fibers should not be needle punched. This is because, conventionally, it has been the idea that filtration with an ultrafine fiber meltblown nonwoven fabric is filtered by the surface. It was thought that when needle punching or hydroentanglement was applied to a melt blown nonwoven fabric of ultrafine fibers, a hole was opened in the nonwoven fabric, so that fine particle dust would pass through the hole and the particulate dust capture efficiency would be reduced. . The inventor has overcome the technical prejudice, and has completed the present invention by a leap of idea that three-dimensionally arranges ultrafine fibers in the coarse layer portion.

Further, if the fiber assembly 6 mainly composed of ultrafine fibers used in the above production method is a melt blown nonwoven fabric or a nonwoven fabric produced by an electrospinning method, the fiber assembly 6 is substantially composed only of ultrafine fibers. Thus, the filtration performance of the obtained non-woven filter material is further improved. Moreover, even if it is a very fine fiber which is difficult to handle, if it is in the form of a nonwoven fabric, it will be easy to handle in the manufacturing process, and the lamination work with other layers will be easy. Moreover, when laminating | stacking on the fiber assembly which should become a coarse layer part, an ultrafine fiber can be uniformly distributed and laminated | stacked, and the quality of the obtained nonwoven fabric is stabilized.

The invention is not limited to the embodiment described above, and can be implemented with various modifications. Although other embodiments of the invention will be described below, in the following description, portions different from the above-described embodiment will be mainly described, and detailed descriptions of the same portions will be omitted. In addition, the embodiments described below can be implemented by combining some of them or replacing some of them.

FIG. 2 is a schematic diagram showing a cross-sectional structure of a nonwoven fabric filtering material 7 according to a second embodiment of the invention. In this embodiment, the point which has the coarse layer part 2 and the dense layer part 3, the point where the ultrafine fiber aggregates 4 and 4 are integrated in the coarse layer part 2, and the ultrafine fiber 41 enters the coarse layer part 2. And the point etc. by which the ultrafine fiber 41 is entangled with the fiber of the coarse layer part 2, and the ultrafine fiber aggregates 4 and 4 are integrated are the same as that of the nonwoven fabric filter material 1 of 1st Embodiment.

The nonwoven fabric filtering material 7 of the second embodiment has an intermediate layer portion 5 between the coarse layer portion 2 and the dense layer portion 3. The intermediate layer part 5 is a layer in which the spatial rate and the fiber diameter are intermediate compared to the coarse layer part and the dense layer part. Thus, the provision of an intermediate layer is advantageous because it improves general dust capturing performance and extends the life.

Further, in the nonwoven fabric filtering material 7 of the second embodiment, the ultrafine fiber aggregates 4 and 4 are located in the coarse layer portion 2 and between the intermediate layer portion 5 and the coarse layer portion 2, that is, downstream of the coarse layer portion. Integrated adjacent to the side.

The nonwoven fabric filtering material 7 of such embodiment can be manufactured by a manufacturing process as shown in FIG. First, in the first step, from the upstream side toward the downstream side, the fiber assembly 21 to be a coarse layer portion, the fiber assembly 6 mainly composed of ultrafine fibers, the fiber assembly 51 to be an intermediate layer portion, Each layer is laminated so that the fiber assembly 31 to be the layer portion is in this order (FIG. 4A).

Then, needle punching is performed with a needle N provided with a barb in a direction from the fiber assembly 6 mainly composed of ultrafine fibers to the fiber assembly 21 to be a coarse layer portion, that is, from the downstream side to the upstream side ( FIG. 4 (b)). Then, with the needle, the ultrafine fibers 41 are drawn into the coarse layer portion 2 and entangled, and the ultrafine fiber assembly 4 and the coarse layer portion 2 are integrated to produce the nonwoven fabric filtering material 7 of the second embodiment ( FIG. 4 (c)).

In this embodiment, in the first step of laminating, the fiber assembly 6 mainly composed of ultrafine fibers is composed of a fiber assembly 21 to be a coarse layer portion and other fiber assemblies (in this embodiment, an intermediate layer and Laminated so as to be sandwiched between the fiber assemblies 51) to be formed. Thus, in the course of the needle punching process, the needle N passes through the fiber assembly 6 mainly composed of ultrafine fibers while pulling and pulling the fibers constituting the intermediate layer 51, and the fiber assembly to be the coarse layer portion. The body 21 will be reached. Then, the fiber aggregate 6 mainly composed of ultrafine fibers is drawn into the fiber aggregate 21 to be the coarse layer portion by the fibers constituting the intermediate layer 51 pulled by the needle N. As a result, the fiber assembly 6 mainly composed of ultrafine fibers is easily loosened and easily fragmented, and the fiber assembly 6 mainly composed of ultrafine fibers is likely to enter the fiber assembly 21 to be a coarse layer portion. Thus, the three-dimensional structure of the ultrafine fibers in the coarse layer portion 2 is more easily promoted.

In particular, when the ultrafine fibers are easily cut by the needle punching or hydroentanglement process, the integration of the ultrafine fiber assembly into the coarse layer portion and the arrangement of the three-dimensional structure are effectively performed. Moreover, also in the case of manufacturing the nonwoven fabric filtering material as in the first embodiment shown in FIG. 1 and FIG. 3, the ultrathin nonwoven fiber layer is upstream of the ultrafine fiber assembly 6 in FIG. If the needle punching process is carried out so as to be arranged on the side, as in the second embodiment, the fibers contained in the ultrathin non-woven fiber layer are used to form the ultrafine fibers and the ultrafine fiber aggregate into the coarse layer portion. 2 can enter.

In the above description of the embodiment, the nonwoven fabric filtering material used for the air cleaner that filters the air supplied to the automobile engine has been described as an example. However, the use of the nonwoven fabric filtering material is not limited to this, and the generator It may be used for the purpose of filtering air supplied to a fuel cell, or may be used for an air cleaner for air conditioning.

  Examples of the present invention will be described below. In addition, this invention is not limited by these Examples.

  In the examples and comparative examples shown below, the filter material in any of the examples is substantially the same in basic fiber material, thickness, basis weight, density gradient between laminated layers, etc. The shape of the filter element and the specifications of the folding are also the same.

Example 1
A melt-blown nonwoven fabric with a basis weight of 5 g / square m, composed of ultrafine fibers made of polypropylene resin having an average fiber diameter of 3 μm, a spatial rate of the coarse layer portion of 96%, a basis weight of 75 g / square m, and an average fiber diameter of 23 μm, A PET non-woven fabric having a two-layer structure having a thickness of 3 mm and a space ratio of the dense layer portion of 92%, a basis weight of 160 g / square m, and an average fiber diameter of 13 μm was prepared. These are laminated so that the melt blown nonwoven fabric, the coarse layer portion, and the dense layer portion are in this order, needle punching is performed from the melt blown nonwoven fabric side, and the nonwoven fabric filtering material 1 of the first embodiment shown in FIG. A corresponding nonwoven filter material was obtained (Example 1). This nonwoven fabric was formed into a folded structure and a frame was attached for the test.

(Example 2)
Compared to Example 1, while making the specifications of each layer of nonwoven fabric used for lamination common, the laminate is so that the meltblown nonwoven fabric of ultrafine fibers is sandwiched between the coarse layer portion and the dense layer portion, from the dense layer portion side. Needle punching was performed toward the coarse layer portion to obtain a nonwoven fabric filter material of Example 2. Example 2 corresponds to a structure in which the intermediate layer portion 5 is omitted from the nonwoven fabric filtering material 7 of the second embodiment shown in FIG.

(Comparative Example 1)
As an example of a non-woven filter material containing no ultrafine fibers, the PET non-woven fabric having a two-layer structure used in the production of Example 1 was subjected to a test as Comparative Example 1 as a non-woven filter material without a melt blown non-woven fabric of ultrafine fibers. .

(Comparative Example 2)
As an example of the prior art of a nonwoven fabric filtering material comprising ultrafine fibers, a melt blown nonwoven fabric of ultrafine fibers is thermally bonded to the upstream side of the coarse layer portion of the PET nonwoven fabric of the two-layer structure used in the production of Example 1, and a comparative example 2 was used for the test.

(Comparative Example 3)
As another example of the prior art of the nonwoven fabric filtering material comprising ultrafine fibers, a melt blown nonwoven fabric of ultrafine fibers is thermally bonded to the downstream side of the dense layer portion of the PET nonwoven fabric having a two-layer structure used in the production of Example 1, The test was conducted as Comparative Example 3.

Experiment: Performance Evaluation for Fine Particle Dust (Carbon Dust) About the obtained filter element, full-life clean efficiency (capture efficiency) test and dust capture amount test for carbon dust according to JIS D1612 (Automobile Air Cleaner Test Method) And the ventilation resistance test was conducted. The test conditions are shown below.

Filter material effective filtration area: 0.18 square m
Test dust: carbon dust (light oil combustion carbon)
Dust supply amount: Carbon dust (0.10 g / min)
Test flow rate: 4.2 cubic m / min Ventilation resistance: Differential pressure between upstream and downstream of filter medium (at start of test)
When the increased ventilation resistance reaches 2.94 kPa, it is defined as full life, and the amount of dust captured so far is defined as the full life capture amount.

The test results are shown in Table 1.
Comparative Example 1 that does not contain ultrafine fibers has the lowest ventilation resistance, but the capture efficiency (cleaning efficiency) of the fine particle (carbon) dust is about 70%, which is a level where improvement in the cleaning efficiency of the fine particle dust is more desired. .

In Comparative Example 2 and Comparative Example 3 in which melt blown nonwoven fabrics of ultrafine fibers were bonded together, the cleaning efficiency of carbon dust exceeded 80% and improved compared to Comparative Example 1, but the airflow resistance increased to about 160 Pa. In order to improve the cleaning efficiency, the ventilation resistance was considerably increased. Further, the carbon dust full life trapping amount is reduced to 50% to 70% compared to Comparative Example 1, and the life of the filter medium with respect to the carbon dust is short. That is, when the ultrafine fiber nonwoven fabric is integrated with the conventional structure as in Comparative Examples 2 and 3, in order to increase the cleaning efficiency, it is necessary to increase the density of the ultrafine fiber nonwoven fabric portion. It was confirmed that the ascending allowance was large, resulting in a shortened filter material life against carbon dust.

In Examples 1 and 2 corresponding to the first embodiment and the second embodiment of the invention, the ultrafine fibers are three-dimensionally arranged in the coarse layer portion, so that the cleaning efficiency of the carbon dust is over 80%, The same improvement in cleaning efficiency as in Comparative Examples 2 and 3 is observed.
On the other hand, in Examples 1 and 2, although the air resistance slightly increased compared to Comparative Example 1, in Comparative Examples 2 and 3, the 20 Pa strong air resistance was increased, compared to Examples 1 and 2. 2, the increase in the airflow resistance of about 10 Pa is suppressed, and the increase in the airflow resistance in Examples 1 and 2 can be halved compared to Comparative Examples 2 and 3.
Furthermore, in Examples 1 and 2, the carbon dust full life trapping amount has increased to about 1.5 times that of Comparative Example 1, and the life of the filter media has been extended while improving the cleaning efficiency against carbon dust. Has been.

As described above, when Examples 1 and 2 are compared with Comparative Examples 2 and 3, the performance can be improved in common in terms of improving the cleaning efficiency of carbon dust by ultrafine fibers. In addition, it is understood that the increase in ventilation resistance is suppressed and the life of the filter medium is extended by the three-dimensional arrangement of the ultrafine fibers in the coarse layer portion.

Moreover, when Example 1 and Example 2 are compared, the result of Example 2 is excellent in any point of clean efficiency, full life capture amount, and ventilation resistance. This is because the fine-fiber melt-blown nonwoven fabric is needle-punched from the dense-layer portion side with the coarse-layer portion and the dense-layer portion sandwiched between the fine-layer fiber-blown nonwoven fabric and the fine-fiber melt-blown nonwoven fabric is fragmented and into the coarse-layer portion. It is presumed that this is a result of the pull-in of the fibers and the three-dimensional arrangement of the fine fibers.

The nonwoven fabric filtering material according to the present invention can be used, for example, for the purpose of filtering air supplied to an automobile engine, and is particularly excellent in the filtration performance of fine particle dust such as carbon dust, and has high industrial utility value.

DESCRIPTION OF SYMBOLS 1, 7 Nonwoven fabric filter material 2 Coarse layer part 3 Dense layer part 4 Ultrafine fiber aggregate 41 Ultrafine fiber 5 Intermediate layer part 6 Ultrafine fiber melt blown nonwoven fabric 21 Fiber aggregate which becomes a coarse layer part 31 Fiber aggregate 51 which becomes a dense layer part Fiber assembly to be the intermediate layer

Claims (4)

A non-woven fabric filter material having a multilayer structure having a density gradient having a coarse layer portion located on the upstream side and a dense layer portion located on the downstream side,
In the coarse layer portion or adjacent to the coarse layer portion, an ultrafine fiber assembly mainly composed of ultrafine fibers is integrated,
At least a part of the ultrafine fibers of the ultrafine fiber assembly enters the coarse layer portion, the fibers constituting the coarse layer portion and the ultrafine fibers entered interlace, and the ultrafine fibers are three-dimensionally arranged in the coarse layer portion. Nonwoven filter material. The nonwoven fabric filtration material according to claim 1, wherein the ultrafine fiber aggregate is a fiber aggregate substantially composed of only ultrafine fibers. 2. At least a part of the ultrafine fiber aggregate is fragmented and integrated in an island shape with respect to the coarse layer part, and a part of the ultrafine fiber aggregate enters the coarse layer part. Or the nonwoven fabric filter material of Claim 2. The nonwoven fabric filtering material according to any one of claims 1 to 3, wherein the fine fiber does not substantially enter the dense layer portion.

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